I know that this is an issue that has been discussed quite extensively and I'll admit that I've not done my due diligence to piece together all the information out there.

However, with that in mind, maybe we can consider this thread a place to compile all that information so it's available at a glance. In short, the problem of coating on film substrates, destined to be used in camera, seems to be a large one.

Polyester/PET

The best material that we all know of is Dupont 583, or 7 mil Estar (melinex) that's coated with a subbing layer and is availabe at the Photographer's Formulary. This is a polyester or PET material.

As I understand it, this was sourced by Jim Browning trying to find a suitable non-staining base for dye-transfer matrices. This material is indeed awesome, but in theory the supply is limited, as are its "format", that is, it's not available in long rolls of thinner widths.

Also, the non-staining aspect is important only for dye-transfer, where the subbing layer should not absorb dye. If we take away this requirement, are there other subbed PET materials that will accept gelatin emulsions?

I seem to recall that Dupont 583 has a very large minimum order (like $100,000+ ??). Perhaps smaller manufacturers would have more reasonable order quantities.

Acetate

What about acetate bases? Denise has posted a about this at the Light Farm (here (http://www.thelightfarm.com/Map/BitsAndPieces/16Mar2010/EmulsionBlog.htm)). The link to Dick Blick is dead, but I believe it was to Grafix's Acetate film. This requires a subbing procedure which she has shown to work well.

So, I take it that this means there isn't an "off the shelf" product that will accept gelatin coatings? They mention a prepared (gel coated) substrate on their website. Can anyone say if this will hold emulsions well? I believe that gmikol* uses these for carbon tissues and the answer to that question might be "not exactly".

The Grafix Acetate (http://www.grafixplastics.com/biodegradable_film.asp) is biodegradable, which doesn't sound too appealing for long-term, archival storage either. How will this stuff hold up in the long run?

Glass

I'm not too worried about glass; it seems that this is a tried and true method that will work in the long run. But glass is only practical in limited situations, at least for most cameras & film holders.

-----------

HRST has built and tested a primitive corona discharge (electron bombardment) machine that at the very least proves that this is possible. This would allow one to coat on plain PET, but it must be done soon after this treatment. Does electron bombardment only work on PET?

What about other manufacturers of PET? Surely DIY emulsionists aren't the only people that need to coat colloids onto polyester film. There are many products that have coatings to better accept inks; what about gelatin?

What would really be the bee's knees would be to find a PET base in 5-7 mil thickness in 12" wide rolls that could fit into something like this (http://www.chemsultants.com/testing-equipment-products/sample-preparation-devices/laboratory-drawdown-coater.aspx) and that would accept gelatin coatings.

Am I missing anything? Looking forward to your input.

*edit: see post 4

Steve Smith

05-09-2012, 02:18 PM

There are many PET materials available in 0.125mm and 0.175mm thicknesses which either have surface coatings or surface treatments to aid the screen printing of inks.

The company I work for uses a lot of this material which we buy in 2' x 3' sheets.

For our purposes, there are two types of coating/treatment. One is suitable for solvent based inks and the other for water based UV cured inks. It is the latter type which I think would be more suitable for emulsion.

A while ago, I collected together some samples for Denise to try out but to my shame, I have just realised that they are probably still in my drawer at work. If you're reading this Denise, please accept my apologies. I will try to post the pieces soon.

Other manufacturers:

http://www.macdermidautotype.com/

http://www.melrose-nl.com/files/SpecsPDFs/GE_Lexan_Film_Brochure.pdf

There are also some polycarbonates and polyester/polycarbonate blends which might be suitable. I will go through what we have at work tomorrow and post other materials/sources.

Note: Mylar is a DuPont trade name, not a general term for polyester.

Steve.

kb3lms

05-09-2012, 02:51 PM

Great idea for a thread to start assembling all this info in one place!

Denise has a supply of Melinex 535 4 mil Estar that works very well. (very similar to the 583, I'm sure) It's a Mylar/PET film subbed on both sides for aqueous applications, which I am interpreting to mean inkjet. She sent me some and I've coated a few feet with good results. DuPont doesn't sell retail - only B2B. However, I have a feeling that the stuff is more available than it appears but you have to know where to look for it. For example, there is a supplier of materials for inkjet printers called LexJet that sells a roll film that they cite as being Melinex:

I have tried the Graphix acetate with less success than Denise had. You can read the thread "Emulsion Stripping" here http://www.apug.org/forums/forum205/101603-emulsion-stripping.html I did finally sucessfully sub the acetate but I had to apply a pre-subbing using nitrocellulose to make it work. The amount of nitrocellulose is very small, though. BTW, I got the PVC to work by using a similar trick with extremely dilute PVC pipe glue but I never tried to coat any real emulsion on it.

The issue with the Graphix acetate is that it is cellulose di-acetate, not cellulose tri-acetate (CTA). In reading the patent literature it looks like the manufacturers in the 1930s gave up on or bypassed di-acetate and went straight to CTA.

Another thing I plan to try is polyester "waterproof" inkjet films intended for silk-screen printing. A few vendors have supplied samples of 4 mil material but I haven't gotten a chance to try coating them yet. The "waterproof" aspect seems to be saying that aqueous inks applied to the film will stay put during processing (whatever process they use) once fully dried down. Thinking about this material was the source of my one comment about inkjet printing the mask in your autochrome/dufaycolor thread.

Finally, it appears that cellulose nitrate needs no subbing at all. But then it has other unique issues.....

-- Jason

gmikol

05-09-2012, 02:57 PM

Acetate

What about acetate bases? Denise has posted a about this at the Light Farm (here (http://www.thelightfarm.com/Map/BitsAndPieces/16Mar2010/EmulsionBlog.htm)). The link to Dick Blick is dead, but I believe it was to Grafix's Acetate film. This requires a subbing procedure which she has shown to work well.

So, I take it that this means there isn't an "off the shelf" product that will accept gelatin coatings? They mention a prepared (gel coated) substrate on their website. Can anyone say if this will hold emulsions well? I believe that gmikol uses these for carbon tissues and the answer to that question might be "not exactly".

The Grafix Acetate (http://www.grafixplastics.com/biodegradable_film.asp) is biodegradable, which doesn't sound too appealing for long-term, archival storage either. How will this stuff hold up in the long run?

The material I use is Grafix' Dura-Lar (http://www.grafixplastics.com/mylar_duralar.asp), not the one that holmburgers' refers to. It's not biodegradable, AFAIK, and claims to be non-yellowing, which would suggest that it is relatively stable. It's definitely a polyester film, according to the MSDS, not CDA or CTA. But the (non-hardened) gelatin can be peeled off the surface relatively easily. I don't have any formalin or other hardening agents to test whether a hardened layer would do the same. There's also "Dura-Lar Wet Media" film, which has some sort of surface treatment, which I think is the other thing Chris refers to, but I don't know anything more about it than that.

Hope that helps to clear things up...

--Greg

kb3lms

05-09-2012, 04:53 PM

Greg,

Any type of mylar has to be subbed using something like the electron bombardment treatment Chris mentions above. IDK if there is a solvent for PET as I have never looked for one. Subbing formulas require a dilute solvent to soften the material and make a more "friendly" layer stick to it.

Graphix, on the Dura-Lar page, mentions a "Prepared (Gel-coated)" material. This might be interesting. Anyone know anything about it?

-- Jason

hrst

05-09-2012, 05:13 PM

The corona treatment (electron bombardment) system is, in principle, very simple. Just create some AC at about 30 kHz and 5 kV(rms), between a "ground plate" and a wire or tube hanging a millimeter or two on the top of the ground plate. Place the plastic on the ground plate and sweep with the tube or wire electrode. You can see the violet glow between the plastic and your electrode.

What I have been struggling with, is that I want to create a simple-to-build, cheap, safe and small system, so that I could make some kind of DIY instructions for everyone to follow. My biggest issue has been finding a source for the transformer needed. I built my own, but it is relatively difficult! It took many attempts to get it working, and then some part of my electronics failed after just a few successful treatments.

Now, the transformers used in microwave ovens do not get to high enough frequencies (the one I tested was fine up to 1 kHz or so; something around 30 kHz would be desirable), and the voltage is a tad low, too (3 kV as opposed to around 5 kV that I found optimum). Those small flyback transformers used in CRT monitors would be fine if they didn't have a rectifier diode built-in, impossible to remove; hence, they give DC, whereas AC is needed.

There are also safety issues that need to be sorted out very carefully.

Otherwise (i.e., when you have the equipment), the corona treatment is a VERY simple and quick process - you "sub" any raw polyester sheet, available just everywhere, in a matter of 30 seconds by sweeping it a few times with this equipment prior to coating. Then you coat within a day or so.

Many other plastics can/must be corona treated, too. It's a widely used process in industry for printing and gluing plastics. Older "flame treatment" is an alternative but probably harder to control.

Those "subbed" polyester roll/sheet products are just corona treated at the factory and then coated with a layer that allows the emulsion to adhere, as the mere corona treatment wouldn't sustain its properties for long enough. But I could make just perfect coatings on raw polyester when freshly corona treated; there was no need for any subbing layer.

dwross

05-09-2012, 07:15 PM

Hi Guys,

Starting a list was a good idea. You can never have too many options at your fingertips.

As for actually making film, I count the substrate part of the process as a solved non-issue. Dupont doesn't sell to the public, but 3M does. 3M 9960 and 3M 9962 are excellent products. 9960 is 6.8 mil polyester, coated on both sides with a hydrophilic subbing, and the perfect thickness for sheet film. 9962 is 3.9 mil and perfect for roll film. The places I talked with that carry it do have a minimum order, but as these things go, it's reasonable. I ended up buying mine from Custom Converting, Inc. in Oceanside, CA, but there are a couple of places on the US east coast, too. I spent $1200, but I have enough film for a lifetime! Interested people who don't really need a lifetime supply of fim could organize a group purchase.

Really, seriously, unless soup-to-nuts DIY is important to you, go with subbed film, at least for now. It will let you concentrate on learning to make great emulsions (although zapping film does sound kinda fun.)

Steve: No worries! Thanks for the thought.
Jason: I didn't have much luck with Dura-Lar or kin, and I think I tried every surface Graphix makes.

Athiril

05-09-2012, 10:55 PM

dwross, if one wanted to some day attempt 61mm width/120 roll, what width would you get 9962 in?

hrst

05-10-2012, 07:30 AM

dwross, if one wanted to some day attempt 61mm width/120 roll, what width would you get 9962 in?

To get good overall coating, you coat larger than final size and then cut after dry. I would leave at least 10 mm extra to both sides. Then, your initial cut does not matter much and can be approximately done with scissors etc.

For example, coat 150 mm wide material and get two strips of 120 film at the same time. Or, coat 120 mm wide and get one 120 and one 35mm strip. Many options here, but I wouldn't bother trying to coat a pre-cut material because of the problems of emulsion leaking out or not filling the whole substrate. Really, it depends on the coating method, but if you coat larger than final you have ALL the coating options available. Most of them (blade, puddle pusher, etc.) rely on the fact that the coating apparatus slides on the top of the very same substrate, meaning that an uncoated area is left over.

For example, if you use a coating blade, 150 mm substrate and 130 mm blade would yield an usable coating of 120 mm quite easily, I think.

It's also nice to get more film at one coating. OTOH, If you try to coat too wide, it starts to get harder, but I think this is not a problem until 200-300 mm.

Many ways to cut, one of the easiest is to place sheets of wood/plastic/metal/anything with straight edges near to each other to form small gaps between them to guide a knife such as a box cutter.

250 mm material would be quite optimum for coating 8x10 sheets. You could coat 2-3 sheets at a time and then cut them separate.

daveandiputra

05-10-2012, 09:35 AM

What about acrylic sheets? Can it be used? This is the easiest to obtain in my place, even easier than thin glass.

dwross

05-10-2012, 10:18 AM

dwross, if one wanted to some day attempt 61mm width/120 roll, what width would you get 9962 in?

Hi,

hrst's answer was very thorough. I can add an example and a couple of comments.

I've been working on standardizing my workflow. I love experimenting and playing, but ever since I finally, really got it that handmade emulsions are up to the task of serious photography, I only want to be out and about with my cameras. That means getting serious about darkroom quality and efficiency. I've made up six identical 5-inch emulsion coaters with 4+ inch /11 cm wells. On film, that makes an almost 5-inch path. I'm using them for film for my WP and every size down, including roll film. That size path is perfect for two rolls of 120 or three rolls of 127. In the attached Whole Plate photo, you can see the fall-off on the edges. The film is 6-3/8 inches wide with a good 5-inch path of emulsion, plus selvage edges. You could either cut off the selvages for smaller formats, or as I'm doing with my WP, incorporate the edges into the final print. By cutting the width to the final format, before coating, I only have to make one cut to length after the emulsion is dry. I do cut off the selvages for roll film. The thinner roll film is easier to cut than the thicker sheet film.

A good method for cutting roll film is to take a roll of commercial film, with a tiny bit of the width trimmed off, and attach it to two pieces of aluminum frame (Nielsen type) with foamcore board holding them apart to the right width. Clamp at the top, hold firmly at the bottom, use a sharp X-acto blade, and perfect film each time.

David,
Acrylic is very hydrophobic. If you want to use it, I'd love to see you develop a good subbing formula/strategy. I hope you do and have great luck.

d

kb3lms

05-10-2012, 10:32 AM

I wouldn't bother trying to coat a pre-cut material because of the problems of emulsion leaking out or not filling the whole substrate.

Yeah, I can confirm that trying to coat a pre-cut to size piece of substrate doesn't work well. You will have to get used to the idea of imprecision and some loss. On the other hand, I have cut leftover edges as small as 35mm single frame "sheets" for testing. Tape the small single frame sheet to a piece of black construction paper if you like to fit in your SLR. A nice thing about doing this is you dont have to try and make and run a roll of film if you are trying to decide on developing procedures, etc, and aren't using large format cameras. You could probably come up with some sort of paper film holder that would fit inthe back of an SLR. (Hmmm) Done this with 120 in my Yashica TLR as well.

I now coat by fastening the substrate to a sheet of 1/4" thick plate glass. I have a few of these as leftover glass shelves from a display case. You can find something cast-off or I believe even new plate (window) glass is not very expensive. It's flat and holds heat well so your emulsion doesn't start to set up on you while you try to coat. (warm the glass a bit before coating)

To help make certain I have covered the area I need to coat without overdoing it, I have made up some paper templates for 120 rolls that I tape to the underside of the glass. Now you can see the template through the substrate and glass and make certain you have covered the proper area and try to avoid creating waste. I have templates made for one roll, two rolls and three rolls.

holmburgers

05-10-2012, 10:49 AM

Fantastic contributions from everyone, thank you all!

So, this is why I started this thread... I had no idea about these 3M products!

Dave, I suspect that acrylic would be prone to the same issues as polyester, but IDK. You could try "roughing up" the surface with a fine sand paper if the gelatin comes off though.

I also like Umut's idea of etching the surface somehow. Ultimately, as hrst suggests, corona treatment, once properly sorted out, is a home-run as well.

Maybe the situation isn't as dire as I thought afterall. Though it would be nice to know if any of these aqueous ink-jet type PET films will take an emulsion well. It seems that if they will, then so should overhead transparency paper like Pictorico.

daveandiputra

05-10-2012, 10:59 AM

David,
Acrylic is very hydrophobic. If you want to use it, I'd love to see you develop a good subbing formula/strategy. I hope you do and have great luck.

d

Any pointers or links to read about it?

dwross

05-10-2012, 11:03 AM

So, this is why I started this thread... I had no idea about these 3M products!

...It seems that if they will, then so should overhead transparency paper like Pictorico.

Don't be afraid to read The Light Farm. :D All info, as I learn it, open source / free of charge. I talked about the 3M films months ago.

If you mean the stuff made for digital negatives (??) , it doesn't work.

d

dwross

05-10-2012, 11:07 AM

Any pointers or links to read about it?

Sorry, no. As far as I know, it's virgin territory and any discoveries could belong to you :). If I were feeling adventurous, I'd probably start with the same subbing as for acetate. But, that's purely a guess.

d

holmburgers

05-10-2012, 11:11 AM

Dont' be afraid to read The Light Farm. :D All info, as I learn it, open source / free of charge. I talked about the 3M films months ago.
d

Yes, shame on me! :sideways:

kb3lms

05-10-2012, 11:24 AM

We'd really need to set up a group purchase of the 3M film. $1200 is a little too much for my budget, although I agree it's the way to go.

Photo Engineer

05-10-2012, 11:25 AM

We might try a purchase of film support just as we did the baryta recently made available via the Formulary.

We could get custom cuts of actual subbed supports currently in use for films. And, they would be in the appropriate thicknesses.

PE

oldfaithful58

05-10-2012, 11:26 AM

http://www.hififilm.com/html/polyester.html
These people are very helpful and may have a suitable product with a commercially/volume acceptable offer
I use them at work for printable films for labels :-)